Compressor bleed control



March 29, 1960 R. N. ABILD COMPRESSOR BLEED CONTROL Original Filed Nov.l5. 1952 ATTORNEY COMPRESSOR BLEED CONTROL Robert N. Abild, New Britain,Conn., assignor to United Y Aircraft Corporation, East Hartford, Conn.,a corporation of Delaware Continuation of application Serial No.320,661, November 15, 1952. This application May 1, 1957, Serial No.656,417

"5 Claims. (Cl. 230-114) This application is a continuation of myco-pending application Serial No. 320,661 filed November 15, 1952 forCompressor Bleed Control, now abandoned.

This invention relates to axial flow compressors, more particularly tocontrols for bleeding axial flow compressors.

Compressors of the axial ow type are made up of a plurality of bladedstages which aot to increase the pressure of gases flowing through thecompressor, each succeeding stage further compressing the gases. Byvarying the number of stages, the pressure ratio, that is the ratio ofcompressor discharge pressure to compressor inlet pressure, can becontrolled. A detrimental characteristic of axial flow compressors isthe tendency to surge or pulsate at low speeds, sometimes resulting inphysical damage to the compressor or its associated structure. Thischaracteristic is due to the fact that the various Stages of thecompressor are designed for maximum efficiency as a unit at oneparticular compressor speed. At a speed lower than the design speed theVarious stages are not correctly matched for the volume of air flowingthrough the compressor. The tendency is for the rst stages to overpumpthe latter stages with the result that the first stages stall out andcause surging or pulsating of the compressor.

The speed at which an axial llow gas turbine power plant can be startedis below the design speed of its compressor and, consequently, startingis very difiicult if surging or pulsating exists. It is known that bybleeding air from appropriate stages of the compressor at speeds belowdesign speed the operating characteristics of the compressorcan bechanged and the detrimental characteristics overcome. More is gained incompressor performance than is lost by dumping or wasting the gaseswhich have been compressed and had work done on them.

Various methods have been used for bleeding axial flow compressors andfor controlling the bleeding thereof. The subject of this invention is acontrol which regulates bleeding as a function of compressor speed andcompressor inlet temperature.

An object of the invention is an axial flow compressor bleed controlwhich closes compressor bleeds over a given speed range so as to obtainmaximum performance from the compressor.

Another object of the invention is an axial flow compressor bleedcontrol which provides stepped, reliable operation and which correctsfor variations of temperature.

Other objects and advantages will be apparent from the specification andclaims, and from the accompanying drawing which illustrates anembodiment of the invention.

In the drawing:

Fig. 1 illustrates an axial ow gas turbine power plant having thecompressor bleed control in accordance with this invention connectedthereto.

' Fig. 2 illustrates the details of one of the compressor bleeds. l

l United States atent O i 2,930,520 ce Patented Mar. 29, 1960 Referringto the drawing in detail, 10 indicates an axial llow gas turbine powerplant having inlet 12, compressor section 14, combustion section 16,turbine section 18 and exhaust nozzle 20. Casing 22 surrounds thecompressor section and has mounted therein rotor 24 comprised of aplurality of discs 26, each disc having blades 28 about its periphery.Interspaced between each row of rotor blades 28 are rows of stator vanes30 which serve to turn the gases flowing through the compressor so thatthey strike the succeeding rotor blades 28 at the most efficient angle.It is to be understood that the compressor can be comprised of anynumber of stages.

Mounted on the forward end of compressor shaft 32 is bevel gear 34 whichdrives bevel gear 36 connected to governor 38 through governor shaft 40.The governor shaft has Ia pair of yweights 42 mounted thereon which vareadapted to be displaced as a function of power plant speed. Theprinciples of such a flyweight governor are well-known in the art.Displacement of the yweights is transmitted to link 44 through plate 46,bearing 48 being interposed between the link and the plate to permitrelative rotational motion therebetween. Spring 50 forces link 44 to theleft to resist displacing action of the flyweights. The right end oflink 44 is connected to lever 52 such that displacement of the linktends to rotate the lever about pivot v54.

Y Pivot 54, the point about which lever 52 rotates, is shifted as afunction of temperature changes in the gases entering inlet 12.Temperature responsive bulb 56 is mounted within inlet 12 and isconnected through line 58 to expansible bellows `60. The bulb, line andbellows are filled with an lappropriate fluid which will respond tochanges in compressor inlet temperature. One end of bellows 60 is fixedas at 62 and the opposite end is connected by link 64 to lever 52 atpivot 54. Changes in the temperature of the gases entering thecompressor result in expansion or contraction of bellows 60 which inturn changes the position of pivot 54 to compensate for temperaturevariations.

The free end of link 52 has a pair of sockets 66 and 68 thereon, eachsocket containing spring backed caps which successively cover a pair ofValves 70 and '72 as the link rotates in a counterclockwise directionabout pivot 54. Sockets 66 and 68 are identical in construction andcomprise housing 74 having valve cap 76 therein loaded by spring 78,each cap being capable of limited axial movement within the housing. Aslever 52 moves counterclockwise about pivot 54 due to displacing actionof iiyweghts 42 caused by an increase in the speed of rotor 24, thevalve cap in socket 66 will close valve 70 and, as counterclockwisemotion of the link continues, the valve cap in socket 68 will closevalve 72. Closing of the valves is sequential, the spacing between thesockets and the valves being such that one valve is closed before theother one. The result is a partial reduction in bleeding as compressorspeed increases, with bleeding being com.- pletely terminated after thecompressor has reached a predetermined speed.

A pair of piston operated, double balanced poppet valves and 82 controlthe gases which actuate the compressor bleeds. Valves 80 and 82 areidentical in construction and operation and, for the purpose ofsimplicity, the details of only one will be described. It is to beunderstood that while the valves function in the same manner they areset in operation at different times.

Valve 80 comprises housing 84 having bores 86, 88 and therein. Portedsleeve 92 is fixed within bore 8S and its end surfaces provide seatingsurfaces for a double balanced poppet plunger 94. Plunger 94 has at oneend an enlargement 96 engaging with bore 86 and at its opposite end anenlargement 98 which is in engagement 3 with bore 90. Spring 100interposed between enlargement 98 and the end wall of bore 90 tends tomaintain plunger 94 in its extreme position to the left, againstshoulder 102 on ported sleeve 92..

Compressor discharge pressure conducted by liner-104 'enters a chamber106 to` the left of enlargement'96 through restricting orifice 108.Valve 70 is also connected to chamber 106 and pressure in the chamber isdischarged through the valve when it is open. Compres sor bleeds 110,the number of which is determined by the volume oi gases to be bled, areconnected by line 112 and port 114 in ported sleeve 92 to chamber 116intermediate the plunger Venlargements 96 and 98. When valve 7i) isopen, compressor bleeds 110 are also open lsince plunger 94 is in theposition shown against shoulder 102, and since chamber 116 is connectedto atmosphere through line 118. Line 118 is also connected to chamf ,ber120 at the right end of plunger 94 within`which splring 100 is located,and vents the chamber to atmose p ere.

When valve 70 is closed by valve cap 76 in socket 66 the pressure withinchamber 106 builds up and pushes on enlargement 96, shifting plunger 94to the right until flange 122 on the plunger is in contact with the leftend of ported sleeve 92. This cuts oi the connection between line 112and line 1l8,'which connected chamber 116 to atmosphere. By means ofpassage 124 compressor dis# charge pressure line 104 is connected toannulus 126 in housing 84 surrounding plunger enlargement 98. Whenplunger 94 shifts to the right, the compressor discharge pressure inthis annulus is admitted to chamber 116 and then to one or morecompressor bleeds 110 through port l114 in ported sleeve 92 and linel112 connecting the valve and the bleed.

Details of the compressor bleeds are shown in Fig. 2. The compressorcasing has two or more cylinders 128 mounted thereon in line with thecompressor stage being bled. Holes 130 in compressor casing 22 connectthe compressor stage to the interior of cylinders 128. These holespreferably are located in the area of stator vanes 30, between rotordiscs 26. Each cylinder contains a piston 132 held by spring 134 in aposition allowing compressor air to be bled to the atmosphere throughopenings 136.

When compressor discharge pressure is admitted to the top side of piston132, as described above, piston 132 is forced down, closing oil?openings 136 and terminating the bleeding of compressor air through theopenings.

Poppet valve 82 functions in the same manner as has been described forpoppet valve 80 and, after valve 72 is closed by valve cap 76 on socket68, poppet valve 82 acts to admitcompressor discharge pressure to acompressor bleed, or bleeds, connected to that poppet valve and closethe bleed to further reduce or completely terminate the bleeding ofcompressor gases.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as dened by the following claims.

I claim:

l. A multi-stage axial llow compressor having a plurality of bleeds forbleeding said compressor between end stages, a pressure responsiveclosure in each of said bleeds for regulating the flow of compressorgases through said bleeds, a fluid connection between the compressordischarge and said bleeds for operating said closures by com pressordischarge pressure, a plurality of valves mounted in parallel in saidfluid connection for controlling the admission of compressor dischargepressure to said bleeds, each valve controlling at least one of saidcompressor bleeds, and means responsive to compressor inlet tempera-Vture and compressor speed for controlling said valves.

2. A multi-stage axial dow compressor having a plu rality of bleeds forbleeding said compressor between end stages, a pressure responsiveclosure in each of said bleeds for regulating the ow of compressor gasesthrough said bleeds, a duid connection between the compressor dischargeand said bleeds for operating said closures by compressor dischargepressure, a plurality of valves mounted in parallel in said fluidconnection for controlling the admission of compressor dischargepressure to said bleeds, each valve controlling at least one of said4compressor bleeds, and means responsive to compressor inlet temperatureand compressor speed for sequentially controlling said valves to givestepped operation of said bleeds.

3. A multi-stage axial dow compressor having a plu-- rality of bleedsforbleeding said compressor between end stages, a piston in each of saidbleeds for regulating the flow of compressor gases through said bleeds,means nor mally positioning said pistons to permit maximum ow throughsaid bleeds, a fluid connection between the compressor discharge andsaid bleeds for admitting compressor discharge pressure to said bleedsto overcome said positioning means and close said bleeds, a plurality ofvalves mounted in parallel in said fluid connection for controlling andadmission of compressor discharge pressure to said bleeds, each valvecontrolling at least one of said compressor bleeds, compressor speedresponsive means for sequentially controlling said valves to give astepped reduction in bleeding as compressor speed increases, andtemperature responsive means for compensating bleeding as a function ofcompressor inlet temperature.

4. A multi-stage axial ilow compressor having a plurality of bleeds forbleeding said compressor between end stages, a piston in each of saidbleeds for regulating the ilow of compressor gases through said bleeds,a iluid connection between the compressor discharge and said bleeds foradmitting compressor discharge pressure to close said bleeds, a valvemounted in said iluid connection for controlling the admission ofcompressor discharge pressure to at least one of said bleeds, compressorspeed responsive means controlling said valve and the admission ofcompressor discharge pressure through said valve to its associatedbleed, at least one additional valve in said fluid connection andconnected to the remaining bleeds, said valve also being controlled bysaid speed responsive means, means for operating said valvessequentially to give stepped closing of said bleeds as compressor speedincreases, and temperature responsive means for compensating bleedingfor variations in compresor inlet temperature.

5. In combination, a multi-stage axial flow compressor comprising arotor and stator having a casing surrounding the rotor, said statorcasing having at least one port formed thereincommunicating interiorlywith the compressor at a selected stage thereof, exhaust means for saidport exhausting air from said selected compressor stage, valve means insaid exhaust means, and control means including speed sensitive meanscontrolling the position of said valve means over the compressoroperating speed range, temperature sensing means responsive tocompressor inlet temperature and means operatively connected with saidtemperature responsive means and said speed sensitive means uandaffecting the point of operation of said exhaust valve means by saidspeed sensitive means vwith changes in compressor inlet temper-References Cited in the le of this patent UNITED VSTATES PATENTS

